Hydrogen gas buildup prevention in hot water heaters

ABSTRACT

A hot water heater includes a controller, a hot water tank and a sensor operatively coupled to the hot water tank and the controller. The sensor is configured to detect use of hot water from the hot water tank. The controller is operative to determine an interval of non-use of hot water from the hot water tank; and enable a drain cycle to withdraw a portion of water from the hot water tank.

BACKGROUND

The present disclosure generally relates to appliances, and moreparticularly to preventing hydrogen gas buildup in a hot water heater.

In a hot water heater system, hydrogen gas can form as a byproduct ofchemical reactions caused by the metals used in the construction of thetanks, particularly when the water in the hot water tank is stagnant.Since hydrogen gas is not soluble in water, any hydrogen gas formed willremain in the water heater plumbing system, tending to rise to thehighest locations in the plumbing system. The hydrogen gas can also betrapped in the lower levels of the plumbing system.

During normal or regular operation of the hot water heater system, theamount of hydrogen gas buildup will be minimal and will tend to bevented from the plumbing system as hot water is discharged from the hotwater tank, either through the dispensing of hot water from a tap, orthe use of hot water by an appliance, such as a dishwasher or washingmachine. However, if the hot water heater system is inactive for anextended period of time, there is a potential for a buildup of hydrogengas generated in the tank.

In order to avoid problems associated with hydrogen gas build up, it isgenerally recommended that when a hot water heater system has beenstagnant for a period of time, such as for example two weeks, the hotwater faucets be opened for several minutes to vent any hydrogen gasthat may have accumulated during the period of non-use.

It would be advantageous to be able to automatically vent a hot waterheater system of any potential hydrogen gas buildup during periods wherethe hot water heating system is not used regularly.

Accordingly, it would be desirable to provide a hot water heater systemthat addresses at least some of the problems identified above.

BRIEF DESCRIPTION OF THE INVENTION

As described herein, the exemplary embodiments overcome one or more ofthe above or other disadvantages known in the art.

One aspect of the exemplary embodiments relates to a hot water heater.In one embodiment, the hot water heater includes a controller, a hotwater tank and a sensor operatively coupled to the hot water tank andthe controller. The sensor is configured to detect withdrawal of hotwater from the hot water tank. The controller is operative in responseto the sensor to detect the occurrence of a stagnant state and initiatethe withdrawal of hot water from the tank in response to such detection.A stagnant state results when the time interval between withdrawals ofwater from the tank is greater than a predetermined interval selected toprevent or limit the generation of hydrogen gas in the hot water tank.

This and other aspects and advantages of the exemplary embodiments willbecome apparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. Moreover, thedrawings are not necessarily drawn to scale and that, unless otherwiseindicated, they are merely intended to conceptually illustrate thestructures and procedures described herein. In addition, any suitablesize, shape or type of elements or materials could be used.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic diagram of an exemplary hot water heater systemincorporating aspects of the present disclosure.

FIG. 2 is a flow chart illustrating an exemplary process flowincorporating aspects of the present disclosure.

FIG. 3 is a schematic diagram of an exemplary hot water heater systemincorporating aspect of the present disclosure.

FIG. 4 is a schematic diagram of another exemplary hot water heatersystem incorporating aspect of the present disclosure.

FIG. 5 is a flow chart illustrating an exemplary process flowincorporating aspects of the present disclosure.

FIG. 6 is a flow chart illustrating another exemplary process flowincorporating aspects of the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE DISCLOSURE

Referring to FIG. 1, an exemplary hot water heater system incorporatingaspects of the disclosed embodiments is generally designated byreference numeral 100. The aspects of the disclosed embodiments aredirected to a hot water heater system that detects when the hot waterheater has not been used for a period of time and automatically drainsenough hot water from the hot water tank to prevent or satisfactorilylimit the generation of hydrogen gas in the tank. Although theembodiments disclosed herein will be described with reference to thedrawings, it should be understood that the embodiments disclosed can beembodied in many alternate forms. In addition, any suitable size, shapeor type of elements or materials could be used.

As shown in FIG. 1, the hot water heater system 100 generally includes ahot water heater 10 and a controller 20. In the embodiment of FIG. 1,the hot water heater 10 includes a reservoir or water storage tank 12for storing water and a heat source 14 for heating the water stored inthe tank 12. The hot water heater 10 includes an inlet 16 for receivingwater into the tank 12. The inlet 16 is typically connected to a watersupply line for a home or building. The hot water heater 10 alsoincludes an outlet 18 for supplying hot water from the tank 12 to thehot water portions of the plumbing system 30 to which the hot waterheater 10 is connected. The plumbing system 30 can be part of aresidential, commercial or other water plumbing system that incorporatesa hot water heater and is generally used to provide a connection betweenthe hot water heater 10 and one or more electrically operated appliances40 that use hot water. Although the plumbing system 30 is referred to inFIG. 1, in one embodiment, there can be a direct connection from the hotwater heater 10 to the appliance 40.

While the aspects of the disclosed embodiments can be applied to anysystem that incorporates a hot water heater 10, for the purposes of thedescription herein, such system will be described as a “plumbing system”or “home.” The hot water heater 10 can be any suitable hot water heaterincluding an electric, gas or hybrid hot water heater. In oneembodiment, the heat source 14 can comprise an electric heating elementsuch as a resistive-type heating element, a gas burner such as a propaneor natural gas burner, a heat pump type of heater, or any other type ofheat source.

As briefly mentioned in the Background, in hot water systems includingsystems of the type illustrated in FIG. 1, when hot water has not beendispensed or discharged from the hot water tank 12 for an extendedperiod of time, hydrogen gas can form as a byproduct of chemicalreactions caused by the metals used in the construction of the tanks. Ifleft unchecked, hydrogen gas can buildup in the hot water heater system100 to an undesirable level. The aspects of the disclosed embodimentsare configured to detect conditions conducive to hydrogen generation,before any significant hydrogen gas buildup has occurred. The timeperiod for such conditions to develop or occur in a hot water heater 10can vary, depending on one or more factors. Examples of such factors,can include, but are not limited to the area of the world and theelevation. Many water heaters come with a warning that hydrogen gasbuild up can occur after about two weeks of inactivity.

In the embodiment shown in FIG. 1, the controller 20 is provided forcontrolling aspects of the hot water heater system 100. In oneembodiment, the controller 20 is configured to detect the occurrence ofcondition of the water in the tank hereinafter referred to as a stagnantstate. A stagnant state is detected when the interval of time betweensuccessive withdrawals or dispensing of water from the tank exceeds apredetermined period which is preferably selected to be of a durationthat is long enough to avoid short cycling or nuisance tripping, butshort enough to prevent the generation of such gas or at least limit thebuild up of such gas in the plumbing system to an acceptable level. Forpurposes of the examples herein, the pre-determined period is selectedto be not greater than fourteen days, although shorter or longer timeperiods can be contemplated, depending upon the particular hot waterheater system application. When the controller 20 detects a stagnantstate of the hot water heater 10, the controller 20 is configured toautomatically enable a drain cycle of the hot water heater 10. A draincycle of the hot water heater 10, as that term is used herein, generallyrefers to a cycle of the hot water heater system 100 that causes hotwater to be discharged from the tank 12, and flow through the plumbingsystem so that hydrogen gas build up cannot occur. A drain cycle cantypically be initiated by opening a hot water valve of the plumbingsystem 30 or running an electrical appliance that is coupled to theplumbing system 30 to withdraw water from the hot water heater. Theaspects of the disclosed embodiments are generally directed toautomatically flushing the hot water tank 12 and associated plumbinglines when the hot water in the hot water heater tank 12 has not or willnot be used for an extended period of time in order to prevent hydrogengas buildup.

In one embodiment, the controller 20 comprises or is coupled to or is incommunication with a processor(s) that is operable to monitor andcontrol the flow of hot water from the hot water tank 12, as well asexecute the processes that are generally described herein. In oneembodiment the controller 20 is comprised of machine-readableinstructions that are executable by one or more processors or othersuitable processing device(s). The processor(s) can include program codeto perform particular tasks and/or data manipulations, as are generallydescribed herein. In one embodiment, the processor(s) can include or becoupled to a memory and input/output devices. The memory typicallycomprises both non-volatile memory, such as semiconductor type randomaccess memory, and non-volatile memory such as a magnetic computer disk.

As is shown in FIG. 1, in one embodiment, the controller 20 is coupledto a user interface 22. The user interface 22 can comprise any suitablecontrol or display that will allow a user to program, set and adjust thefunctions and settings of the hot water heater system 100, as aregenerally described herein. In one embodiment, the user interface 22comprises or includes a control panel 26 that allows a user to programthe system 100 and set the hydrogen gas buildup prevention functions asare further described herein. These functions can include, but are notlimited to, setting a hot water heater stagnation time period threshold,setting a vacation mode and programming the system 100 to activate anappliance 40 connected to the system 100 to enable a drain cycle. In oneembodiment, the user interface 22 can include a display interface, suchas a touch screen display. In alternate embodiments, the user interface22 can include buttons or switches for manipulating and programming thesettings of the system 100. In one embodiment, the user interface 22comprises or is part of a control panel for the hot water heater 10.Alternatively, the user interface 22 can be part of a control panel foran appliance 40. The user interface 22 can also be located remotely fromthe hot water heater 10, and can be accessible through a computingdevice or a web based interface. For example, aspects of the disclosedembodiments allow the controller 20 and control panel 26 to be accessedand programmed using a mobile communication device 330, as will befurther described herein.

As is illustrated in FIG. 1, in one embodiment, the system 100 includesone or more sensors 24 for monitoring the state of the hot water in thehot water tank 12. The sensor 24 is generally configured to provide oneor more signals or commands to the controller 20 that will allow thecontroller 20 to detect a stagnant state, because water has not beenwithdrawn from the hot water tank 12 for an extended period of time. Inone embodiment, the sensor(s) 24 can comprises water flow monitors fordetecting the flow of water into, out of, or both into and out of thehot water tank 12. In this example, the sensor(s) 24 can be coupled tothe tank 12 or one or both of the inlet 16 and outlet 18.

In another embodiment, the sensor(s) 24 can be configured to sense theactivation of one or more loads of the hot water heater 10. The loads ofthe hot water heater 10 generally include any appliance 40 that utilizeshot water. In one embodiment, the sensor(s) 24 can also comprise atemperature measuring device that is configured to monitor and detect atemperature of the water in the hot water tank 12.

The sensor 24 can be coupled to the controller 20 via a wired orwireless communication connection or interface. For purposes of thedescription herein, wireless communication connections and interfacescan include, but are not limited to, wireless radio, WiFi, Bluetooth,Zigbee and ethernet wireless type devices and interfaces. In oneembodiment, the sensor 24 can be integrated with the controller 20.

In one embodiment, the controller 20 can include, or be coupled to aclock/timer device 28. The clock/timer device 28 can comprise anysuitable timing device that is capable of monitoring and providing realtime data, providing an event clock or timing mechanism, or providingboth real time and event timing capabilities. In one embodiment, thecontroller 20 is configured to use the clock/timer 28 to determine astagnant state of the hot water heater 10, such as by determining anelapsed time since a last use of the hot water from the hot water tank12. Although the clock/timer 28 will generally be referred to as asingle clock or timing device, the clock/timer 28 can also includemultiple clock/timer device. For example, the clock/timer 28 couldinclude one clock/timer for monitoring an elapsed time since a last useof the hot water from the tank 12, and another clock/timer formonitoring a time since a change in state of the sensor 24.

By providing information corresponding to the state of the hot water inthe hot water tank 12 to the controller 20, a stagnant state of the hotwater tank 12 can be determined FIG. 2 illustrates one example of aprocess flow incorporating aspects of the disclosed embodiments. In oneembodiment, the controller 20 monitors 202 the state of the sensor(s)24. Based on an indication from the sensor 24, the controller 20 isconfigured to determine 204 the time or time interval since the last useor flow of hot water from the tank 12, the use being one that issufficient to drain enough hot water from the hot water tank to preventor satisfactorily limit the generation of hydrogen gas in the tank.Generally, a flow amounting to approximately 0.5 to 1 gallons, orlasting approximately one to five minutes is a sufficient use.

In one embodiment, determining the time, or a time interval, since thelast use of the hot water from the tank 12 comprises comparing a currentclock time to a clock time of last use. A difference between these twovalues can be used to determine if a pre-determined time threshold orinterval has been exceeded. Alternatively, the clock/timer 28 can starta counter that is used to determine an elapsed period since the lastuse. The controller 20 is configured to determine 206 whether apredetermined time period or threshold time interval of non-use is metor exceeded. Since it is generally understood that the potential forhydrogen gas buildup in a typical domestic hot water heater system canoccur after approximately two weeks of non-use, the predetermined timeperiod or threshold time interval is selected to be not greater than twoweeks. For example, a period of a few days or one week can be used asthe threshold time interval. Alternatively, any suitable time period canbe used that will prevent hydrogen gas buildup in the hot water heater10 can be used as the predetermined time period or threshold timeinterval.

If it is determined 206 that the predetermined time period has notelapsed, in one embodiment, the controller 20 continues to monitor 202the state of the sensor(s) 24. If the predetermined time period haselapsed, indicating that the hot water heater 10 is in a stagnant state,the controller 20 is configured to enable 208 a drain cycle of the hotwater tank 12. The drain cycle is generally configured to allow asufficient amount of hot water to be drawn from the hot water tank 12 inorder to prevent any hydrogen gas buildup. In one embodiment, the amountof hot water drained from the hot water tank 12 in a drain cycle is inthe range of approximately 0.5 to and including 1.0 gallons. Inalternate embodiments, any suitable amount of hot water can be dispensedfrom the hot water tank 12 to ensure that any hydrogen gas that hasbuilt up in the tank 12 and plumbing system 30 has been vented ordispersed.

In one embodiment, the drain cycle can be an activation of one or moreof the appliances 40 coupled to the hot water heater system 100 towithdraw water from the hot water heater. For example, in oneembodiment, when the controller 20 determines 206 that there has notbeen any use of hot water from the tank 12 for a period of approximatelyone week, the controller 20, which is communicatively coupled to the hotwater consuming appliances 40, can activate an appliance such as adishwasher, to run through a hot water cycle for a few minutes and thendrain the water. The cycle should be sufficient to drain an amount ofwater from the tank 12 that will also flush any built-up hydrogen gasfrom the tank 12. After the cycle is complete, the controller 20continues to monitor 202 and measure 204 the time period of inactivity.

One embodiment of a system 300 incorporating aspects of the disclosedembodiments is illustrated in FIG. 3. In this example, the controller 20is communicatively coupled, via wired or wireless connections, to thehot water heater 10, sensor 24, timer 28, the one or more appliances 40and communication gateway 320. In this example, the appliances 40include a dishwasher 42, a washer 44 and an electronically controlledhot water discharge valve 46. In one embodiment, the hot water dischargevalve 46 is an electronically controlled valve coupled to a hot waterfaucet or other outlet. Activation of the valve 46 can allow hot waterto be discharged from the hot water tank 12. Each of the appliances 40is a consumer of hot water from the hot water heater 10, and whenoperated will allow hot water to be discharged from the hot water tank12 shown in FIG. 1. The hot water is discharged from the hot waterheater 10 to each of the appliances 40 through the plumbing system 30that fluidly couples the hot water heater 10 to each of the appliances40 in a manner that will be generally understood.

In the embodiment shown in FIG. 3, the controller 20 is communicativelycoupled to a communication gateway or interface 320. The communicationgateway 320 allows the homeowner or other user to communicate with,program and operate the controller 20 and hot water heater system 100shown in FIG. 1 through one or both of a computing device 324 and mobilecommunication device 330. The communication connection between thedevice 324 and controller 20 can be via a wired or wireless connection,as is otherwise described herein. When using a mobile communicationdevice 330, the communication gateway 320 allows the user to communicatewith the controller 20 through a remote connection and network. In thisexample, the communication interface or gateway 320 includes a homerouter 322, a computing or communication device 324, a broadbandcommunication interface or modem 326 and a communication network 328.The devices 324 and 330 can comprise any suitable computing orcommunication devices, such as for example, a home computer, a mobilephone, a smartphone, a pad or tablet type device. Generally, the devices324 and 330 will comprise any device that is capable of communicatingwith the controller 20 over a wired or wireless connection, as aregenerally known, in a suitable communication format. The network 328 cancomprise any suitable communication network, such as for example theInternet or a cellular communication network. In one embodiment, a usercan utilize a mobile communication device 330, such as a smartphone, tocommunicate with the controller 20 to program the system 300 from aremote location to monitor the hot water system 100, detect a stagnationstate of the hot water heater 10, and periodically cause hot water to bedischarged from the hot water tank 12 to prevent hydrogen gas buildup.

In one embodiment, referring to FIG. 4, the hot water heater system 100includes, is part of, or is coupled to a home energy gateway or manager(HEG) 50. The home energy manager 50 is communicatively coupled to oneor more of the exemplary appliances 40 to initiate or activate a hotwater consumption cycle of one or more of the appliances 40 to preventhydrogen gas buildup. In one embodiment, the home energy manager 50 ispart of a home energy management system. Home energy management (HEM)systems are generally used to reduce energy consumption in homes andbuildings. A typical home energy management system is configured tocommunicate with and control electrical appliances in homes andbuildings. These electrical appliances can include appliances 40 thatmake use of hot water from the hot water heater 10. Some functions of ahome energy management system, and the home energy manager 50 are tocreate a network of appliances 40 in the home or building, monitor theusage of such appliances, record and store information, enable consumerinterface with all appliances in the home, and set preferences andoperation modes for the appliances. In the embodiment shown in FIG. 4,the home energy manager 50 is coupled to the controller 20 in a suitablemanner, including wired or wireless connections. In alternateembodiments, the home energy manager 50 can be integrated with orcomprise the controller 20, the user interface 22 or both the controller20 and user interface 22, and include a connection to the sensor 24 asis generally described herein.

In one embodiment, appliances 40 that are communicatively coupled to thehome energy manager 50 can be automatically controlled to run hot water,which will create water movement in the hot water tank 12. As anillustrative example, if a homeowner is expecting to be away from thehome for an extended period of time, the homeowner can program the homeenergy manager 50 to activate one or more of the appliances 40 to runhot water at predetermined time intervals. At each time interval, anappliance 40, such as a dishwasher 42, can be controlled to withdraw asmall amount of hot water from the hot water heater and then drain it.If the valves and drains of the appliances 40 cannot be separatelycontrolled, the dishwasher 42 can be controlled to run through asuitable dish washing cycle(s) that uses hot water.

In one embodiment, the controller 20 and user interface 22 allow a userto program certain modes or states of the hot water system 100 thatindicate periods of non-use and enable the automatic filling anddraining of the hot water tank 12 to prevent hydrogen gas buildup. Forexample, in one embodiment, referring to FIG. 5, a vacation mode orstate of the hot water heater system 100 can be detected or set 502. Theterm “vacation mode” generally refers to a programmable state of the hotwater heater 10 that indicates that hot water from the hot water tankwill not be regularly used. The aspects of the disclosed embodimentsallow the hot water heater system 100 shown in FIG. 1, for example, tobe programmed as part of the vacation mode, to activate a drain cycle ofthe hot water heater 10 at predetermined time intervals, without firstneeding to determine that the hot water heater 10 is in a stagnantstate. In one embodiment, the vacation mode state can be set using theuser interface 22 of FIG. 1 to program one or more of the hot waterheater 10, an appliance 40 and controller 20. The vacation mode statewill be recognized or detected by the controller 20. With reference toFIG. 3, in one embodiment, the vacation mode state can be set using oneor both of the computing device 324 and mobile device 330.

In one embodiment, after the activation of the vacation mode state isdetected 502, the clock/timer 28 is activated 504. This can includestarting a counter that either counts up or counts down. In oneembodiment, the controller 20 is configured to monitor 506 the elapsedtime and determine 508 if the elapsed time exceeds a predetermined timeinterval. If yes, the controller 20 is configured to enable 510 a draincycle, such as by enabling the activation of an appliance 40 to utilizehot water. In one embodiment, before enabling 510 the drain cycle, thecontroller 20 can confirm that the vacation mode is still set. Once thedrain cycle is complete, the controller 20 can confirm that the vacationmode is still set 502 and reset or restart 504 the timer 28. If it isdetermined 508 that the elapsed time has not exceeded the predeterminedtime interval, the controller 20 continues to monitor 506 the elapsedtime. In one embodiment, if the elapsed time has not exceeded thepredetermined time interval, the controller 20 can confirm that thevacation mode is still set before continuing to monitor 506 the elapsedtime.

Referring to FIG. 6, in an embodiment where the sensor 24 comprises awater temperature sensor, the controller 20 is configured to monitor 602the temperature of the water in the hot water tank 12 in order todetermine whether the hot water heater 10 is in a stagnant state. Inthis embodiment, the controller 20 can be configured to detectdeviations or changes of the temperature of the hot water in the hotwater tank 12. Temperature changes of the water in the hot water tank 12that exceed a nominal or predetermined temperature deviation, generallyreferred to as dramatic changes, can be indicative of withdrawal of hotwater from the hot water tank 12. A nominal deviation or change isgenerally indicative of the natural drop in temperature of the water inthe hot water tank 12, which requires reheating of the water. Forexample, in one embodiment, the controller 20 can be configured tomonitor the temperature of the water in the hot water tank every 10minutes. If the detected temperature drop after 10 minutes is less thanapproximately 5 degrees, it can be determined that there is no waterflow from the hot water tank 12, and the water is stagnant. In anotherembodiment, in an exemplary hot water heater 10 operating in an energyefficient mode, if a drop in temperature of the water on the order ofapproximately 0.2 degrees Fahrenheit occurs over an approximately 2minute time period, the controller 20 is configured to determine thatthere is normal or regular water flow from the hot water tank 12,indicating that a stagnant state has not occurred. A larger flow mightbe determined by a temperature drop of approximately 8 degrees inapproximately 10 minutes.

Alternatively, the controller 20 or home energy manager 50 can beconfigured to dynamically determine an average temperature ortemperature change of the hot water in the tank 12 during normal orregular operation and use the dynamically determined average temperatureto determine a stagnant state. In one embodiment, dynamicallydetermining the average temperature or temperature change can comprisetaking temperature measurements over a predetermined time interval andtaking an average of the temperature readings. In one embodiment, thevacation mode can be used as an initial learning algorithm. For example,in one embodiment, when the controller 20 first detects that a vacationmode of the system has been set or such other suitable indication thatthe hot water heater 10 will not be used for an extended period, thecontroller 20 is configured to periodically read the water temperatureof the water in the water heater 10 and determine how fast the watertemp inside water heater decreases. In this example, the controller 20is configured to read the water temperature approximately every minute.If the controller 20 determines that over a period of time such asapproximately 10 minutes the water temperature drops only approximately0.1 degrees Fahrenheit, then this temperature/time change factor of 0.1degrees F./10 minutes, is set as the baseline for temperature change dueto environmental loss and not water usage. This baseline can be used todetermine a stagnant state. For example, if the controller 20 determinesthat over a period of time, such as one week, there has been atemperature drop corresponding to the baseline temperature/time changefactor of 0.1 degrees F. in 10 minutes, the controller 20 can beconfigured to identify a stagnant state and automatically run some waterthrough the dishwasher or washer. Although this dynamic process can berun when a vacation or such similar mode is first set, in oneembodiment, the controller 10 can be configured to determine when thehot water heater 10 has been inactive for a predetermined period oftime, and the initiate the dynamic learning process. For example, whilethe vacation mode can be used as the initial learning algorithm fordynamic learning process, in a situation where a vacation mode is notset, the aspects of the disclosed embodiments can detect that hot wateris not being used and initiate a learning mode or state. In thisembodiment, using dynamic process is used to determine thetemperature/time factor and monitor the hot water heater 10 for astagnant state. As another example of dynamically determining thetemperature of the hot water heater 10, the controller 20, which in thisexample can include a real time clock, may read and store watertemperature readings every minute or so. Based on the temperaturereadings, the controller 20 may determine that most water usage occursbetween 5 pm and 10 pm on weekdays, because of large drops of watertemperature over short periods of time. In this example, the controller20 uses the temperature changes during the time period of midnight to 5PM as the baseline of water temperature loss due to the environment. Thetemperature changes determined during this period of time can be set asthe baseline or temperature/time change factor determining when hotwater is not being used. For example, in one embodiment, the usermanually enters the time period(s) during which most of the water isused. For instance, this could include one time period of 7 AM-8 AM andanother time period of 5 PM-10 PM. The controller 20 can use any of theremaining time periods, such as 8 AM-5 PM and 10 PM-12 PM, to determinethe baseline temperature/time change factor. The temperature drop orloss due to the environment can also be different for different seasonsof the year, such as for example the seasons corresponding to the monthsof January-March, April-June, July-September and, October-December. Thecontroller 20 can be configured to determine baseline temperature/timechange factors for each of the seasons.

In one embodiment, the controller 20 is configured to determine andrecord the time of the day, or periods of time, when water draw from thehot water heater 10 is detected. As is otherwise described herein, adefault indication of hot water draw from the hot water tank 10 is anapproximate 0.2 degree temperature drop in approximately 2 minutes, oran approximately 8 degree temperature drop in approximately 10 minutes.The controller 20 can records the times of water draw for aper-determined period of time, such as one week. The controller 20 candetermine the time periods of no water draw and determine the averagetemperature drop of water due to environment during these no water drawtime periods. The value of this new average temperature drop can bedesignated as a maximum temperature loss per time period allowed toestablish a stagnant state.

In one embodiment, determining whether the hot water heater 10 is in astagnant state can include determining 604 whether a change intemperature of the hot water exceeds a predetermined thresholdtemperature change value or range, such as the baseline temperature/timechange factor or maximum temperature loss per time period.

If it is determined 604 that a temperature change of the hot waterexceeds the threshold value, this generally indicates that the hot waterheater 10 is not in a stagnant state and the controller 20 can continueto monitor 602 the water temperature. In one embodiment, monitoring 602can include setting a timer. At the expiration of a predetermined timeperiod, the controller 20 can determine 604 whether there has been atemperature change within the predetermined time interval that exceedsthe predetermined temperature threshold change. If yes, indicating thatthe hot water from the hot water tank 12 has been used, the controller20 can reset the timer and continue to monitor 602 the watertemperature.

If it is determined 604 that there has not been a change in temperatureof the water in the hot water tank 12 exceeding the predeterminedtemperature threshold value, indicating a no-flow state, in oneembodiment, the controller 20 determines 606 whether a predeterminedtime period since the last use of the hot water from the hot water tank12 has elapsed. The determining step 606 can use the elapsed time of thetimer in step 602 to determine in the predetermined time period haselapsed. In one embodiment, once the no-flow state is determined in 604,or the vacation mode is set, another timer can be started. Thedetermining step 606 can use an elapsed time of this other timer indetermining whether the predetermined time period has lapsed. Inalternate embodiments, the step of determining 606 can include anysuitable method for determining a time interval since the last use ofhot water, including the process described with respect to steps 204 and206 in FIG. 2.

If it is determined 606 that the predetermined time value is met orexceeded, in one embodiment, the controller 20 initiates 608 a hot waterusage cycle of an appliance 40. Otherwise, the controller 20 continuesto monitor 602 the hot water temperature to determine 604, 606 whetherthere is a change of temperature that exceeds a nominal threshold valuewithin a predetermined time period, indicating use of the hot water.

In one embodiment, determining whether the hot water heater 10 is in astagnant state can include monitoring the powering of the heat source14, such as the heating elements. If there is limited or no power drawor consumption by the heat source 14 for a predetermined time period,such as one week, the controller 20 is configured to determine that thehot water heater 10 is in a stagnant state. While the heat source 14will consume some energy in response to environmental heat loss of thehot water heater 10, the amount of energy required to reheat the waterdue to environmental heat loss will typically be distinguishable or lessthan the amount of energy require to heat the water after a water draw.For example, in one embodiment, the controller 20 is configured todetect the time that a heating source 14 is powered on. If the heatsource 14 is on due to a water draw, the length of time the heat source14 is on, such as approximately 5-8 minutes for example, will generallybe greater than the period of time the heat source 14 is on due toenvironmental heat loss, which can be approximately in the range of 2 to4 minutes. The controller 20 can detect the time the heat source 14 ison, compare the detected time value to a predetermined threshold, anddetermine if the hot water heater 10 is in a stagnant state.

The system 100 and controller 20 of FIG. 1 are generally configured toutilize program storage devices embodying machine-readable programsource code that is adapted to cause the apparatus to perform andexecute the method steps and processes disclosed herein. The programstorage devices incorporating aspects of the disclosed embodiments maybe devised, made and used as a component of a machine utilizing optics,magnetic properties and/or electronics to perform the procedures andmethods disclosed herein. In alternate embodiments, the program storagedevices may include magnetic media, such as a diskette, disk, memorystick or computer hard drive, which is readable and executable by acomputer. In other alternate embodiments, the program storage devicescould include optical disks, read-only-memory (“ROM”) floppy disks andsemiconductor materials and chips. The computer program or softwareincorporating the processes and method steps incorporating aspects ofthe disclosed embodiments may be stored in one or more computer systemsor on an otherwise conventional program storage device.

The exemplary embodiments described herein provide a system forautomatically determining when the hot water in a hot water tank 12 hasnot been used or is stagnant. In order to prevent or eliminate anyhydrogen gas buildup in the hot water heater system and associatedplumbing, a fill and drain cycle of the hot water heater can be run.This can include automatically operating an electrically operatedappliance fluidly coupled to the hot water heater. The aspects of thedisclosed embodiments can automatically detect periods of non-use of thehot water heater based on times of use of the hot water heater, changesin temperature of the water in the hot water tank, or the setting ofpreprogrammed modes of the hot water heater or appliances. The periodicoperation of the hot water heater system should prevent any buildup ofhydrogen gas.

Thus, while there have been shown and described and pointed outfundamental novel features of the invention as applied to the exemplaryembodiments thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

What is claimed is:
 1. A hot water heater comprising: a controller; ahot water tank; and a sensor operatively coupled to the hot water tankand the controller, the controller being operative in response to thesensor to detect use of hot water from the hot water tank to determinean interval of non-use of hot water from the hot water tank; and enablea drain cycle to withdraw a portion of water from the hot water tankupon such determination.
 2. The hot water heater of claim 1, wherein thesensor comprises a water flow sensor and wherein the interval of non-useis determined if a time interval of no water flow from the hot watertank exceeds a predetermined time threshold.
 3. The hot water heater ofclaim 1, wherein the sensor comprises a water temperature sensor,wherein the interval of non-use is determined if any change intemperature of the water in the hot water tank during a pre-determinedtime interval does not exceed a pre-determined temperature changethreshold value.
 4. The hot water heater of claim 1, further comprisinga user interface operatively coupled to the controller, the userinterface enabling a vacation mode of the hot water heater to be set,and wherein the controller is configured to detect the vacation mode ofthe hot water heater and enable the drain cycle to withdraw a portion ofwater from the hot water tank at predetermined time intervals.
 5. Thehot water heater of claim 4, further comprising a wireless interfaceoperatively coupling the user interface and the controller.
 6. The hotwater heater of claim 1, further comprising a wireless radio connectionbetween the controller and the sensor.
 7. The hot water heater of claim1, further comprising an electrically operated hot water using applianceoperatively coupled to the controller, wherein enabling the drain cyclecomprises enabling operation of the electrically operated appliance towithdraw water from the water heater.
 8. A hot water heater systemcomprising: a hot water heater; and a controller coupled to the hotwater heater, the controller operative to: determine a stagnant state ofthe hot water heater; and enable a drain cycle of the hot water heater.9. The hot water heater system of claim 8, wherein the drain cycle isenabled at predetermined time intervals during the stagnant state. 10.The hot water heater system of claim 8, further comprising a water flowsensor operatively coupled between the controller and the hot waterheater and wherein the controller is operative to: detect a flow of hotwater from the hot water heater; and determine an elapsed time from thedetection of the detected flow; and the stagnant state being indicatedwhen the elapsed time is greater than the predetermined threshold time.11. The hot water heater system of claim 8, further comprising a watertemperature sensor operatively coupled between the controller and thehot water heater and wherein the controller is operative to determinethe stagnant state by monitoring a temperature of hot water in the hotwater heater; and wherein the stagnant state being indicated when thetemperature change does not exceed a predetermined temperature changethreshold value during a time interval of predetermined duration. 12.The hot water heater system of claim 8, further comprising: an applianceoperatively coupled to the hot water heater and the controller; whereinthe controller is operative to enable the appliance to withdraw waterfrom the hot water heater upon determination of a stagnant state. 13.The hot water heater system of claim 12, wherein the appliance comprisesa dishwasher, a washer, or an electronically controlled hot waterdischarge valve.
 14. The hot water heater system of claim 8, furthercomprising a user interface operatively coupled to the controller, theuser interface enabling user selection of a vacation mode state of thehot water heater, wherein the controller is operative during thevacation mode to enable the drain cycle of the hot water heater atpredetermined time intervals.
 15. The hot water heater system of claim14, further comprising an electrically operated appliance with a controlpanel operatively coupled to the controller, the user interfacecomprising the control panel.
 16. The hot water heater system of claim14, further comprising a wireless interface operatively coupling theuser interface and controller.
 17. The hot water heater system of claim16, wherein the user interface comprises a mobile communication device.18. The hot water heater system of claim 8, further comprising a homeenergy management system, the controller comprising a home energymanager of the home energy system.
 19. A hot water heater systemcomprising: a hot water heater; an appliance coupled to the hot waterheater and configured to withdraw hot water from the hot water heater;and a home energy manager coupled to the hot water heater and theappliance, wherein the home energy manager is configured to enable theappliance to withdraw hot water from the hot water heater atpredetermined time intervals.
 20. The hot water heater system of claim19, wherein the home energy manager is configured to detect a stagnantstate of the hot water heater and enable the appliance to withdraw hotwater from the hot water heater upon detection of the stagnant state.